Bad throttle response after slowing down

[Anonymous]

Last autumn the bike started to behave little odd after running a while on high rpms. I didn?t care much then but now it?s getting more dangerous. When I hit the throttle after slowing down there is no response for a while. If I keep the throttle open it will response after a few seconds. If I pull the clutch the response is however immediate. This is behavior is escalating and is becoming a real problem when riding. I have no help by the engine to raise the bike when riding a narrow curve. Last summer the bike did not have this behavior. The only mode it had was that it was stalling when I wanted it to idle after going at high rpms for a while. I do not now if that problem is related to the current, but I thought I mention it. The problem was very minor and the bike idled fine just by a twitch on the throttle. Nothing has been changed on the bike since it ran perfectly smooth. The bike is a almost stock GS 550 E - 82. The only mod is home made exhaust, but the bike ran nice with them last year. Where should I start looking? Fuel line?; Carbs?; Electrics?; Compression?

[volks28]

Re: Bad throttle response after slowing down

I won't be much help, but I do have a similar problem. The bike will not idle after a 20 minute ride at 4-5k (highway). Other than that it was running fine

Members of this board has suggested me to try opening the gas cap a bit (i.e. holding it with some tape) to get the ventilation going. Haven't had a chance to try it, but it's my suggestion

[HiSPL]

Have you changed your spark plugs lately?


Could be the case of your plugs running cooler than they used to when new allowing carbon/soot buildup on deceleration. When you hit the gas it takes a second for the plugs to clean up and start firing again.

Just a shot in the dark on my part, but sometimes it's the simple things that tend to get overlooked.... 8)

Good luck...

[Poot]

either that, or the jets could be mucked up a little bit.


pilot jet is for anything upto 1/4 throttle, and that would be my bet as to the issue, although im not 100%

[duaneage]

First things first.

Check for the common vacuum leaks. Inspect the intake boots and spray WD-40 or carb cleaner spray around the rubbers while the engine is running and see if there a leak.

How is the petcock? If the petcock diaphram is going bad you will loose fuel and without fuel it will lean out ( especially on turns when the carbs lean over). Dirty fuel filter? Dirty Air Filter? Dirty bike ( just kidding)?

I think your petcock is having problems. Try the bike with the petcock in the PRI position and see if that fixes it.

These things are easy, cheap and necessary to check first.

[Anonymous]

Tanks a lot for all your replies.

First things first.

Check for the common vacuum leaks. Inspect the intake boots and spray WD-40 or carb cleaner spray around the rubbers while the engine is running and see if there a leak.

How is the petcock? If the petcock diaphram is going bad you will loose fuel and without fuel it will lean out ( especially on turns when the carbs lean over). Dirty fuel filter? Dirty Air Filter? Dirty bike ( just kidding)?

I think your petcock is having problems. Try the bike with the petcock in the PRI position and see if that fixes it.

These things are easy, cheap and necessary to check first.

No leaks, Im not sure about the petcock, I'll try it in PRI position on my way home today, Air filter is fine, but perhaps the fuel filter needs to be changed. I'll by a new one on my way home aswell.

Have you changed your spark plugs lately?


Could be the case of your plugs running cooler than they used to when new allowing carbon/soot buildup on deceleration. When you hit the gas it takes a second for the plugs to clean up and start firing again.

Just a shot in the dark on my part, but sometimes it's the simple things that tend to get overlooked....

Good luck...

I have new spark plugs. However, since the problem started I changed to a set softer plugs. Are you suggesting I should have tried harder ones?

either that, or the jets could be mucked up a little bit.


pilot jet is for anything upto 1/4 throttle, and that would be my bet as to the issue, although im not 100%

The jets are cleaned.

Members of this board has suggested me to try opening the gas cap a bit (i.e. holding it with some tape) to get the ventilation going. Haven't had a chance to try it, but it's my suggestion

I will try this too. I remeber I thought about it reading old posts, but I forgotten about it. Thanks for reminding me.

I'll let you know the results on Monday.

[Anonymous]

Now I tried all the stuff suggested, but with no luck. Pri position on petcock did not help, not did the opened gas cap. Following other threads gave me new ideas. I saw some suggestions on dimensions on fuel lines. I do not now what dimension I have, only that it is stock and I just cut it to fit an inline gas filter. The filter is a paper type, one thread here suggest that this a bad thing. Does anyone else have bad experience with paper gas filters? My fuel line is very long since I didn't shorten it when fitting the gas filter. May this also cause trouble?

[redliner1973]

Yes to both questions. Paper cartridge type filters are a no-no with a gravity feed type system. Get a free-flow type designed for M/C use. Also, too long of a line invites kinks and turns. It does not take much kink to slow fuel enough to starve the carbs. use 8mm (5/16") fuel line. Not 7mm (1/4"). Also check to make sure Petcock is flowing a good amount. if it is not changing your situation on 'prime', take tank off to make sure there is a free flow of fuel. you would be suprised at how easily they can clog. Try that and let us know what you find.

[Anonymous]

Problem solved. I changed the fuel filter to a non paper type and shortened the fuel line a little. The bike runs much better, but I have to check the plugs again. With a bad filter the bike (in my opinion) should have starved and run lean, but the plug reading during the time I had problems was:
No. 1 good
No. 2-4 just a little rich

How come

The bike still doesn?t want to idle after a heavy ride, but that?s a problem I can live with.

Thanks a lot for all advises.

[gspaul]

If you did not do a plug chop , like killing the moter at sustained wide throttle opening,then a plug check,the act of slowing down reduce's the amount of fuel required,so the colour your getting on the plug's would be more related to your pilot mix screw's.
I do not advise any kind of inline filter,It's graverty feed ,the filter in the tank will do the job.
If any rust in the tank ,clean her out.